Aircraft, such as drones, constantly need to determine their in-air position. Although GPS systems are a popular solution to this problem, in some cases, GPS is insufficient and/or unattractive. For example, in an urban canyon environment (e.g., where the aircraft is surrounded by tall buildings), the accuracy of GPS decreases significantly. In particular, GPS is not as accurate in determining altitude as it is with latitude and longitude. Some other techniques for determining altitude (e.g., using barometers) do not work well in applications when the propellers and/or rotors disturb the barometers. Having equipment which can accurately and reliably determine altitude is an important ability in aircrafts. Therefore, new techniques for determining an in-air position (e.g., without using GPS and/or barometers) would be desirable.